Titanium dioxide-containing synthetic filament having improved properties textile products made therefrom and method of imparting said improved properties

ABSTRACT

Titanium dioxide-containing synthetic filament having an improved surface properties which contains dispersed throughout its structure in an amount of 0.01- 1 percent by weight, based on said filament, titanium dioxide particles consisting essentially of particles not greater than 7 microns in particle diameter, of which 10-70 percent by weight is coarse particle titanium dioxide of 0.8- 7 microns in particle diameter, textile products made therefrom and a method of imparting said improved properties.

United States Patent Inventors YasushiKatagiri 1-55-2, Zendana-cho, Mizuho-ku;

Teruo Obata, 2-33, Hasho-dori, Mizuhoku; Masahiko Sugiura, 32, Tahakura-cho, Atsuta-ku; Ryoichi Yasuda, 1-40, Shigocho, Minami-ku, all of Nagoya, Japan Appl. No. 712,447

Filed Mar. 12,1968

Patented Oct. 26, 1971 TITANIUM DIOXIDE-CONTAINING SYNTHETIC FILAMENT I'IAVING IMPROVED PROPERTIES, TEXTILE PRODUCTS MADE THEREFROM AND METHOD OF IMPARTING SAID IMPROVED PROPERTIES 7 Claims, 6 Drawing Figs.

U.S.Cl 161/174, 260/37 Int. Cl 002g 3/02 Field of Search 161/174; 260/40, 37, 39

% LIJ Z 2 OO LLI Z to I O0 I II CD [56] References Cited UNITED STATES PATENTS 2,000,671 5/1935 Singmaster 161/174 2,233,344 2/1941 Helm et al. 161/174 2,566,441 9/1951 Camras 161/174 2,706,674 4/1955 Rothrock 264/206 Primary Examiner--Morris Sussman Attorney-Sherman and Shalloway O '2'O'4'O'6'O'8'O'IOO PROPORTION OF COARSE PARTICLE IOe II TITANIUM DIOXIDE [%/TI'O2] CONTENT OF T102 O3%/FH AMENT PATENTEU E 3,616,184

SHEET NF 3 WEIGHT RATIO OF THE PARTICLES (%I I I 0012014016018 2 3 4 5 6 T PARTICLE DIAMETER Il- I 0 0126405 OBI '2 '3 A '5 6 T PARTICLE DIAMETER IP-I WEIGHT RATIO OF THE PARTICLES T-fi I R OO204D-608I 234567 PARTICLE DIAMETER (f WEIGHT RATIO OF THE PARTICLES PATENTEUUEI 26 [9?! 3,616,184

SHEET'EUF 3 OAT O 0.3

. \TTTORO 0.2

0 2'0 4'0 6O 8O IOO PROPORTION OF COARSE PART|CLE(O.8-7, TITANIUM DIOXIDE [%/TIOz) CONTENT OF TiOZ O.3/o/ FILAMENT 0 20 4'0 6'0 8'0 IOO PROPORTION OF COARSE PARTICLE (O.8-7 u) TITANIUM DIOXIDE [%/TiO2] CONTENT OF TiO2 0.3% FILAMENT PATENTEDUGI 26 I971 SHEET 3 BF 3 O O 3 T5 CONTENT OF TiO2 0.3%/F|LAMENT TITANIUM DIOXIDE-CONTAINING SYNTHETIC FILAMENT HAVING IMPROVED PROPERTIES, TEXTILE PRODUCTS MADE THEREFROM AND METHOD OF IMPAR'IING SAID IMPROVED PROPERTIES This invention relates to titanium dioxide-containing synthetic filaments which, as compared with the conventional product, have improved surface properties as a result of its content of titanium dioxide of improved characteristics, textile products made therefrom and a method of imparting said improved properties. More particularly, the invention relates to synthetic filaments containing titanium dioxide having improved characteristics in the particle distribution and in which the surface properties have been improved, which is characterized in that there are contained dispersed in the melt-spun synthetic filaments, in an amount of about 0.01-1 percent by weight, and preferably b 0.1-0.7 percent by weight, based on the weight of said filament, titanium dioxide particles substantially having a particle diameter not greater than 7 microns, and generally about 0.1-7 microns, of which particles 10-70 percent by weight, and preferably -60 percent by weight of the said titanium dioxide, consists of coarse particles of particle diameter 0.8-7 microns, and preferably 1-7 microns, it being preferred that two peaks in the particle size distribution are present, one each in the two ranges of (1) a particle diameter range of the coarse particles, including those whose particle diameter are preferably in the range l-6 microns, and more preferably 2-4 microns, and (2) a particle diameter range of particles smaller said coarse particles, including those whose particle diameters are preferably in the range 0.2-0.5 microns; to the textile products made therefrom; and to a method of imparting such improved properties.

A most important advantage of the improvement is that the smoothness of the synthetic filaments is notably improved without causing an undesirable luster effect or loss of brightness in filaments. The term smoothness as used herein means easiness in processing of these filaments into fabrics and knittings depending upon the lower dynamic friction resulting when the filaments are passed over guide surfaces at high speed. Hence, the drawbacks such as filament break during its reeling, warping, weaving or knitting and losses in the quality of the final textile product due to the filaments being subjected to an excessively great variation in tension are removed to a still greater extent than the conventional titanium dioxide-containing synthetic filaments. In addition, there are such advantages as that the easiness in the aforesaid processing is enhanced still further and that there is not fear of causing the loss of the brightness of color development in its dyed products.

It has been a well-known practice to incorporate titanium dioxide as a so-called delustrant" in the synthetic textile fibers produced by melt-spinning such fiber-forming synthetic polymers as polyamides, polyesters and polyolefins.

In this case, the mean value of the particle size of the titanium dioxide incorporated in the synthetic textile filaments is not greater than 0.5 micron, and usually in the range of about 0.2-0.3 micron. The most important reason why its particle size is not greater than 0.5 micron is that the delustring effect of titanium dioxide is greatly influenced by the particle size of the titanium dioxide. Namely, the covering power of titanium dioxide, the criterion of its delustring effect, is greatest when its particle diameter is about 0.3-0.4 micron and decreases as the particle size becomes greater than this range. Since, therefore, the delustring effect decreases when the larger size titanium dioxide particles are employed and thus has proved to be undesirable from the standpoint of its delustring effect which is the primary purpose for using titanium dioxide, the larger size particles are not employed usually.

0n the other hand, it is known that filaments break and losses in the quality of the end products are prevented during the operations such as reeling, warping, weaving or knitting if there is an increase of the content in the synthetic filament of the finely divided particles of titanium dioxide of the aforesaid particle size, as presently being actually used. In addition, an enhancement of the easiness in processing can be expected. However, depending upon the use to which the fiber is to be put, the use of titanium dioxide in an amount in excess of its proper amount as a delustrant causes an excessive loss of the brightness in the synthetic filament and not only has the reverse effect of reducing its merchandise value but also causes the loss of the brightness in color development when it is dyed and further leads to undesirably high losses in tensile properties. Hence, as a matter of course, a restriction is imposed on the extent to which an increase can be made in the content in the synthetic filament of the titanium dioxide of which particle size is less than 0.5 micron in mean particle diameter, and usually in the range of 0.2-0.3 micron as are used in practice, in an attempt to achieve adequate improvements in such as the prevention of filament break and loss in quality as well as enhancement of processability. Consequently, the achievement of still further advancement in the aforesaid improvement could not be hoped for.

With a view to overcoming the limitation imposed on the improvement due to such a restriction as to the content of titanium dioxide in the filament and as a result provide a titanium dioxide-containing synthetic filament having the previously noted numerous improved advantages wherein a proper degree of delustrings effect of the brightness of the synthetic filament is manifested without the loss of brightness to an undesirably excessive degree and hence in which the smoothness of the filament is improved still further without the necessity of increasing the content of "the titanium dioxide excessively, we investigated the relationship between the particle size and its distribution of titanium dioxide and the surface characteristics and brightness of filament. In consequence, we have found, as hereinbefore noted, a new type of titanium dioxide by which the aforesaid object can be achieved. Namely, we have found a method wherein by the conjoint use of titanium dioxide of a particle size greater than that customarily employed, i.e., coarse particles having a particle diameter 0.8-7 microns whose delustring effect is small, with the conventional titanium dioxide of a mean particle diameter of 0.2 -0.5 micron whose delustring effect is great, it is possible to obtain fibers which would. effectively demonstrate the two properties of aforesaid smoothness and brightness. BY this finding the coarse particle titanium dioxide which had hitherto been regarded as being practically worthless from the standpoint of its delustring effect is employed from a new angle. Hence, this is a novel invention.

It is therefore the primary object of this invention to over come the above-mentioned drawback or loss in brightness of filament inevitably resulting from the content of titanium dioxide in the conventional method by a method which could not have been expected from the common knowledge of the art, and to provide a titanium dioxide-containing synthetic filament and the textile products made therefrom having improved filament surface characteristics and its smoothness as compared with the conventional products.

Another object of the invention is to provide an improved process for production of such filaments.

A further object is to provide titanium dioxide having a special particle size distribution, which has not been used hitherto in achieving such an improvement and which is especially suited for utilization therefor.

Other objects and advantages of the invention will be apparent from the following description.

The titanium dioxide-containing synthetic filament of this invention contains dispersed throughout its structure in an amount of 0.01-1 percent, and preferably 0.1-0.7 percent, by weight, based on said filament, titanium dioxide having a particle size not greater than 7 microns; 10 -70 percent by weight, and preferably 15-60 percent by weight, of the total titanium dioxide particles contained in the said filament being coarse particles having a particle diameter from 0.8 to 7 microns, and preferably in the range of [-7 microns. Because the filament as a rough surface, an area of contact of it with a guide surface is reduced, and consequently the effective yarn coefficient of dynamic friction is reduced. Hence, the smoothness of a filament is improved because of the lower dynamic friction.

Further, it is particularly preferred that titanium dioxide should have two peaks in its particle size distribution, each in the particle diameter range of the aforesaid coarse particles and the other that of particles smaller than said coarse particles.

Titanium dioxide of this type has not per se been proposed heretofore nor has it been used as a delustrant.

As the titanium dioxide of the hereinabove described type, a preferred and typical one employed in this invention is one wherein one of said two peaks in particle size distribution falls within the particle diameter range of 0.2-0.5 micron and the other peaks fall within the particle diameter range of 1-6 microns.

As example of this type of titanium dioxide will be more fully described with reference to the accompanying drawing, in which:

FIG. I is a rough drawing illustrating one example of the particle size distribution of the new type titanium dioxide suitable for use in this invention.

FIG. 2 is a rough drawing similar to that of FIG. 1 of a titanium dioxide having conventional particle size distribution, such as has been employed heretofore as a delustrant.

FIG. 3 is a similar rough drawing illustrating one example of a titanium dioxide having a particle size as was not utilized heretofore as a delustrant.

FIGS. 4, 5 and 6 are graphs showing the relationships between the proportion of coarse particles contained in titanium dioxide containing coarse particles of 0.8-7 micron in amounts as substantially employed in the invention and the coefficient of dynamic friction of yarn, brightness of filaments and abrasiveness of metal by the filament containing the titanium dioxide.

The titanium dioxide employed in this invention, as illustrated in FIG. 1, has two peaks in particle size distribution, peak A within the particle diameter range of the coarse particles and peak B within that of the particles smaller in diameter thanthe coarse particles. In FIG. 1 is illustrated an instance where the peak A falls within the range of the particles having particle diameters of 0.2-0.5 micron and peak B falls within the range of the particles having particle diameters of 1-6 microns.

FIG. 2 illustrates an example of a titanium dioxide such as has been employed heretofore as a delustrant which has a peak A within a range of particle diameters of 0.2-0.5 micron, while FIG. 3 shows an example of a titanium dioxide of coarse particles which was heretofore regarded as being undesirable for use as a delustrant in the point of its delustring effect and hence has not employed. Its particle size distribution peak 8 falls within a range of the particle diameter of l-6 microns.

In general, the particle size distribution of titanium dioxide is principally influenced and determined by a hydrolytic step during its preparation, and therefore titanium dioxide with a particle size distribution having essentially a single peak is usually produced in accordance with the generally known crystal particle formation phenomenon, while there is a difference in the position of the peak, as shown in FIGS. 2 and 3.

The titanium dioxide such as illustrated in FIGS. 2 and 3 are not capable of achieving the objects of this invention when they are each used alone.

Needless to say, the type of titanium dioxide such as shown in FIG. I is generally not available commercially. However, it can be obtained by blending in arbitrary proportion the usual types of titanium dioxide such as shown, for example, in FIGS. 2 and 3; or by crushing a part of a titanium dioxide having the particle size distribution shown in FIG. 3 or one whose peak B is still larger and thereafter blending the so crushed particles with the remaining large particles in arbitrary proportion, or by changing the conditions for the crystal particle formation during the preparation of the particles at an interim point of the formation process; but the method of just blending together the two types, i.e., those consisting of respectively coarse and finely divided particles, is the easiest way of obtaining the titanium dioxide employed in this invention, and is to be recommended. Hence, the titanium dioxide to be employed in this invention may be prepared by any means so long as aforesaid requisites are satisfied. In obtaining the desired titanium dioxide by blending in an arbitrary proportion two or more classes of the single peak-type titanium dioxides, needless to say, the mixing may be carried out not only in just the dried state of these titanium dioxide but may also be carried out in their slurry state. From the operational standpoint it is easier to carry out the mixing in the slurry state.

The most desirable type of titanium dioxide to be employed in this invention is such as is shown in FIG. I, but the results intended by this invention cannot be expected by the use of the usually employed titanium dioxide having a mean particle diameter of 0.2-0.3 micron, and on the order of about 0.5 micron even in the case of the largest particles, and in which the content of the coarse particle titanium dioxide of above 0.8 micron is less than [0 percent. On the other hand, when the particle diameter of the titanium dioxide exceeds 7 microns, it cannot be employed, because there is a tendency to the occurrence of break of the synthetic filament containing such a titanium dioxide as well as a pronounced decline in easiness of drawing during filament-making process.

FIG. 4 shows the relationship between the changes in the proportion of coarse-particle titanium dioxide having particle diameter of 018-7 microns to the total content of titanium dioxide and the changes in the coefficient of dynamic friction when a 30 denier-6 filament nylon yarn was passed over at I00 meters per minute while in contact with a metal. It is apparent from this figure that the coefficient of dynamic friction decreases remarkably as the proportion of the coarse-particle titanium dioxide becomes about 10 percent, thus resulting in an improvement in the yam's smoothness as demonstrated by its slidability over the metal and consequently in an improvement of the processability of the yarn. On the other hand, the relationship between the brightness of the yarn and the proportion of the coarse-particle titanium dioxide in this case is as shown in FIG. 5. It is seen that as the proportion of the coarse particles becomes greater, the brightness tends to become excessive and the delustring effect as intended by the addition of titanium dioxide decreases to an excessive degree. On the other hand, as shown in FIG. 6, if the proportion of the coarse particle titanium dioxide is increased, it is seen that the abrasiveness of a metal by the yarn when the yarn is passed over while in contact with the metal tends to increase, which is not desirable. That the filament of this invention which contains the coarse-particle titanium dioxide, has the unique properties as shown in FIGS. 4-6 is, as apparent from FIG. 7, due to the fact that its surface has been roughened by the coarse-particle titanium dioxide. Thus, when the delustring efi'ect and the metal abrasiveness by yarn are considered, the amount to be occupied by the coarse-particle titanium dioxide having a particle diameter of 0.8-7 microns in total content in the filament of the titanium dioxide having a particle diameter not greater than 7 microns should properly be I0-70 percent by weight,

and preferably 15-60 percent by weight, of the total content in the filament of titanium dioxide.

In incorporating the specific titanium dioxide in the fiberforming synthetic polymer in this invention, titanium dioxide particles of particle size and particle size distribution as will satisfy the previously described specific conditions are added to the reaction system prior to the completion of the polymerization reaction, preferably during that period of the intermediate stage of the polymerization reaction when a low polymer is beingprincipally fonned in the reaction system or prior to this period, for example, before beginning of the polymerization, at the beginning or the initial to the intermediate stages of the polymerization reaction, the addition being made in a slurry state using, say, water and/or a monomer, and in an amount such that the said titanium dioxide particles are contained in the resulting polymer in a range of 0.01-1 percent by weight. After. completion of the polymerization reaction, the resulting fiber-forming synthetic polymer is made into filaments by melt-spinning.

Needless to say, it is desired that the titanium dioxide is contained in the filament in a homogeneously dispersed state. For example, sincethe coarse particle component corresponding to the peak Bshown in FIG. 1 settles to the bottom is a very short period of time, great care must be exercised to ensure that the titanium dioxide is well dispersed in the titanium dioxide slurry as well as in handling the prepared slurry.

For improving the dispersibility, Good results are had by the use of a suitableinorganic or organic dispersing agent As such dispersing agents, included are the inorganic dispersing agents such, for example, as sodium pyrophosphate, sodium polyphosphate and sodium polymetaphosphate, and the organic dispersing agents such, for example, as the condensation products of polyoxyethylene glycol and an alkyl phenol of the following formula:

wherein n is an integer from 3 to 16 and x is an integer from The polymers towhich this invention can be applied are the fiber-forming synthetic polymers which include the copolymers and blended polymers as well, and include the polyamide type polymers, the polyester type polymers and the polyolefin type polymers.

The following nonlimitative examples further illustrate the present invention. The measurement values for coefficient of dynamic friction, brightness, abrasiveness, unwinding tension of pirn, tensile strength, fluctuation of yarn tension during warping and yarn break duringknitting of tricot, as referred to in the examples as well as the drawings, were determined in the following manner.

Brightness 05 Gram of the sample is placed ina 8:2 phenol-methanol mixture and dissolved therein by heating at 50 C. This solution is then measured for its transmittance using a photoelectric photometer (manufactured by Hitachi Ltd., Japan; Model rPw-4 The transmittance indicated was adopted as the measure of the brightness of the yarn,

It is undesirable for this brightness to. be too small or too great. The optimum value. will depend on the use to which the yarn is to be put, but when-a semidull yarn is desiredwith an addition of the titanium dioxide inan amount of 0.3-0.5 percent, a value on the order of 20-65 percent is most suitable. Abrasiveness The abrasiveness is a. value obtained by passing over the synthetic fiber in contact with a copper wire (guide) under the following conditions:

Speed of yarn travel 200 m./min. Time of travel 40 min. Tension guide front 7.5 grams guide rear grams The amount of wear of the copper wire is obtained by the depth of focus of a microscope and this is indicated in microns t). This abrasiveness should be less than 100 microns, and preferably less than about 70microns, the lower, the better. Coefficient of Dynamic Friction The coefficient of dynamic friction is obtained by passing over a synthetic yarn in contact with a metallic rod underthe following conditions, measuring the yarn tension at the front and rear sides of the metallic rod and substitution of the so obtained values in Ammontons expression to obtain the coefficient of dynamic friction (pd).

Speed of yarn 300 m./min. Original tension (T,,) 5 grams Angle of contact with the metallic rod (9) 1r radian T Ammontons expression =e about 0.25.

Unwinding Tension of Pim A synthetic yarn forming a pim is unwound from said pirn at a linear speed of 300 meters per minute and the yarn tension between the topmost part of the pirn and a guide disposed at a distance 30 centimeters therefrom perpendicularly of said pirn is measured.

Tensile Strength A Schoppers fiber tensile tester is used and pulling a 50-cm. length yarn at a speed of 50 centimeters per minute, the maximum strength (G) is measured.

Separately, yarn 900 meters in length is dried in an electrically heated constant-temperature camber of l05t2 C. until it is absolutely dried, after which it is: weighed and its denier (D) is obtained. The tensile strength is calculated by the following expression:

Tensile strength G/D Fluctuation in Yarn Tension During Warping The tension of the yarns immediately prior to their being wound up on the beam during warping is measured under the following conditions and the standard deviation is calculated.

Yarn speed 300 mJmin. Number of yarns 620 Tension compensator Washer type Yarn Break During Knitting ofTricot The number of yarn breaks occurring during the knitting of halftricot under the following conditions are determined.

Knit density 58 courses/inch Number of rotations 800 r.p.m.

Knit width 200 inches EXAMPLE 1 Six parts by weight of titanium dioxide of the type shownin FIG. 2, which is usually used as a delustrant, (except that the mean particle diameter was 0.25 micron) and 4 parts by weight of a coarse-particle titanium dioxide of the type shown in FIG. 3 (exceptthat the peak position was at 2 microns) were added to 90 parts by weight of water, after which the titanium dioxide was dispersedwith stirring, thereby obtaining a l0-percent aqueous slurry of titanium dioxide. The so obtainedaqueous slurry of titanium dioxide was added along with a small amount of a titanium dioxide dispersing agent to an aqueous percent epsiloncaprolactam solution, in an amount such that the content of titanium dioxide would become 0.3 percentby weight, after which the mixture was stirred to prepare a compounded lactam aqueous solution for polymerizationuse. The compounded lactam aqueous solution was then melt polymerized in customary manner and the intended polyamide chips incorporated. with titanium dioxide was obtained. The so obtained polyamide chips were usedand a 30 denier-6 filament yarn was obtained by the usual meltspinning method. THe properties of the so obtained yarn are shown in table 1, below. By way of comparison, also shown in table I, are theinstances of a yarn obtained in exactly the same manner except that it contained 0.3 percent by weightof the heretofore used titanium dioxide of the type. shown in FIG. 2 (comparison 1), a yarn obtained in exactly the same manner except that it contained 0.3 percent by weight of only the titanium dioxide of coarse particles (comparison 2) and a yarn obtained in exactly manner but containing no titanium dioxide at all (Control).

TABLE I Exani- Compari- Compari- Example Control ple 1 son 1 son 2 Titanium dioxide:

Particle size (It) )7 1. 75 0. 8-7 Peak of particle size distribution i) 0. 25 & 2 025 2 Course particle size (it) 0.8-7 0. 8-1. 75 0. 87 Proportion of course particles of total amount in filament (percent) 40 4 100 Properties of the yarn spun:

Content of titanium dioxide in yarn (percent by weight) 0.3 0.3 0.3 Number of coarse particles (1-7u) in yarn 350 3 s75 Coefficient of dynamic friction 2 (between yarn and metal) 0.41 O. 23 0. 35 0.21 Brightness (percent) 98 56 37 2 Abrasiveness 01.)-.. 1O 49 35 195 Tensile strength (g./d.) 5. 23 5.05 5. 10 4. 81 Unwinding tension of pirn (g.) 5. 9 3. 5. 5 3. 3 Variation in yarn tension during Wa rping (g.):

X 6. 4 4. 2 6. 1 4. 0 c 1. 1 0.2 0.8 0. 2 Yarn break during tricot knitting (times/50 m.) 13. 1 1. 3 7. 8 0. 9

be obsewed. The titanium dioxide of 1-7 microns was counted.

As demonstrated by the results shown in table I, above, 5 titanium dioxides used were those whose particle diameter when the warping and knitting of a tricot were carried out using the yarn in example 1, the value of the yarn tension and its variation were small, and improvements form the operational standpoint and the quality of the product were achieved.

EXAMPLES 2-7 Titanium dioxide usually used as a delustrant of the type shown in FIG. 2 (mean particle diameter 0.25 micron) and coarse-particle titanium dioxide of the type shown in FIG. 3 were mixed in varied proportions, and to these mixture water was added to obtain various slurries of titanium dioxide. THese slurries were used and, as in example 1, 30 denier-6 filament polyamide yarns containing the titanium dioxide havwas 0.1-7 microns and of which 40 percent by weight of total content of titanium dioxide in the filament consisted of particles having a diameter of 0.8-7 microns, but the titanium dioxide particle size distribution peak (B) was varied. By way of comparison, also shown are instances where said peak was at below 1 micron and at above 7 microns (comparisons 3 and 4).

As demonstrated by the results shown in table lll,it can be seen that even though the proportion of the coarse-particle titanium dioxide to this total content in the filament is the same, the properties of the filament will vary depending upon the position of the peak (B) in the titanium dioxide particle size distribution, i.e., the particle size and its distribution of the coarse-particle titanium dioxide. When the position of the peak (B) of the coarse particle in the titanium dioxide particle ing two peaks in this particle size distribution were obtained. 40 I THe properties f these yams are Shown in table 1|, below size distribution 18 at 0.5 microns, the brightness and abrasive- TABLE II Example 2 3 4 5 6 7 Titanium dioxide:

Particle size i)- 7 7 7 )7 7 )7 Peak particle size distribution:

0. 25 0. 25 0. 25 0. 25 0. 25 0. 25 i 2 2 2 i 3 5 Coarse particle size i) 0.8-7 0.8-7 0. 8-7 0.8-7 0. 8-7 Proportion of coarse particle to total content in filament 10 50 50 50 Properties of yarn spun:

Content of titanium dioxide in filament (percent by weight 0. 3 0.3 0.3 0.3 0.3 0.3 No. of coarse particles (1-7u) in filamerit 66 158 455 211 597 512 Coefficient of dynamic frictional (between yarn and metal). 0. 20 0.27 O. 25 0. 25 0. 24 0. 25 Brightness (percent). 44 58 52 62 f5 Abrasiveness i) 48 4o 63 50 54 Tensile strength (g./d.). 5.10 5.10 5.01 5.03 5.00 4.98 Unwinding tension of prin (g) 5.6 4. 3 3. 6 3. .l 3. 5 3, 7 Variation in yarn tension during warpmg (g):

X 6.1 5.7 4.7 5.2 4.9 4.4 a 0.7 0. 5 0.2 0.3 0.2 0. 5 Yam break during tricot knit ing (times/50 m.) 4. 2 2.1 1.0 1.6 1.1 1.8

It can be seen from the results shown in table II, above, that ness are satisfactory, but the results anticipated for the coeffithe titanium dioxide-containing filaments of this invention excient dynamic friction and processability are not obtained. On hibit excellent qualities and that the position of the peak (B) the other hand, when the position of the peak (B) of the of the coarse particle in the titanium dioxide particle size discoarse particle in the titanium dioxide particle size distributribution and the content of the coarse particles (0.8-7 in tion exceeds the upper limit prescribed by the invention and is the filaments can be modified and adjusted. at 8 microns, good results can be obtained with respect to the coefficient of dynamic friction and variation in yarn tension EXAMPLES 3.4 1 during warping, but the yarn break during warping and knitting of tricot and abrasiveness are great, and moreover i table belowxafe Show the results Obtained When the decline in tensile strength takes place, and hence is not desiraexperiment was carried out as in example i, except that the ble from the standpoint of the quality of the product.

TABLE III Com- Compari- Exam- Exam- Exam- Examparison pie pIe ple ple son Experiment 3 8 9 10 11 4 Peak (B) of coarse particle in particle size distribution (a) 0. 5 1 2 4 6 8 Yarn properties:

Coefficient of dynamic friction 0.31 0. 26 0.23 24 0. 22 0, 18 Brightness (percent) 41 46 53 62 65 83 Abrasiveness (11)..." 41 43 49 55 90 113 Tensile strength (g./d.) 5. 20 5. 5.05 4.81 4. 72 4. 55 Unwinding tension of pirn (g.) 4. 2 3.8 3. 5 3. 4 3.1 3. 1 Variation of yarn tension during warp- 1ng (g.):

EXAMPLE 12 A titanium dioxide slurry was obtained by adding to 90 parts of water 5 parts of titanium dioxide of the type shown in FIG. 2 (mean particle diameter 0.25 micron) which is usually used as a delustrant and 5 parts of coarse-particle titanium oxide of the type shown in FIG. 3 (mean particle diameter 1 micron). The so obtained slurry was used and, as in example 1, polyamide chips containing 0.3 percent of titanium dioxide having two peaks in the particle size distribution was obtained. A 15 denier-I filament yarn was obtained using the foregoing polyamide chips. When this yarn was used and womens hose were knit therefrom, the variation in the yarn tension was small and its was possible to make hose of uniform length. Again, the meshes and loops of the hose were uniform.

On the other hand, hose which were knit from yam produced by the same manufacturing process as this yarn and containing titanium dioxide of the type usually used as a delustrant in an amount equal to that of this yarn were not of uniform dimension and the size of the loops was also irregular.

EXAMPLE 13 A 30 denier-6 filament polyamide yarn was obtained, as in example I, using titanium dioxide which, being made up of particles of diameter not greater than 7 microns and containing coarse-particle titanium dioxide in a proportion of 30 percent by weight of the total titanium dioxide, but had only one peak in the titanium dioxide particle size distribution. THe properties of this yarn are shown in table IV. Further, by way of comparison, the results obtained in the case of a yarn in which was used titanium dioxide of the type shown in FIG. 1 whose proportion of coarse-particle titanium dioxide of 0.8-7

TABLE IV Com- Com- Exampie paripari- Experiment 13 son 5 son 1 Titanium dioxide:

Particle size (a) J 7 7 1. 75 Peak of particle size distribution:

A (p) 0.43 0.43 0. B (p) 3 Proportion of coarse-particle titanium dioxide to its total content in filament (percent) 30 4 Content of titanium dioxide in filament (percent) 0 3 0.3 0 3 Yarn properties:

Coefficient of dynamic friction 0. 29 0. 25 0.35 Brightness (percent) 42 52 37 Abrasiveness (p) 45 51 Unwiuding tension of prin (g.).. 5.1 3. 6 5. 5 Yarn break during warping (trmes/ 50 m.) 5. 1 1 6 Variation in tension during tricot knitting (g.):

microns to its total content in the filament was 30 percent and in which two peaks in the titanium dioxide particle size distribution were present (comparison 5) and the results of comparison I previously shown in table I are also shown. In all cases the content in the filament of the: titanium dioxide was 0.3 percent. As apparent form the results shown in table IV, while the effects of this invention can be expected even thought there is only one peak in particle size distribution so 25 long as coarse-particle titanium dioxide of 0.8-7 microns is contained, the effects are less than when there are two peaks.

We claim: 1. A titanium dioxide-containing melt-spun polyamide filament having improved surface propenties, characterized in 30 that said filament contains, dispersed throughout its structure in an amount of 0.0l-l percent by weight, based on said filament, titanium dioxide particles consisting essentially of particles not greater than 7 microns in particle diameter, of which l-70 percent by weight is coarse particle titanium dioxide of 35 08-7 microns in particle diameter, said titanium dioxide particles having a first distribution peak in the particle size distribution in the range of Oi-0.5 micronsand a second distribution peak in the particle size distribution In the range of l-6 microns.

2. THe synthetic filament according to claim 1 wherein said titanium dioxide particles consists essentially of those of particle diameters 0.1-7 microns of which 15-60 percent by weight consists of said coarse particles of particle diameter range l-7 microns.

3. A synthetic filament according to claim 1 wherein the second of said peaks falls within the range of 2-5 microns.

4. A synthetic filament according to claim 1 wherein said titanium dioxide particles are contained dispersed in the melt spun synthetic filament in an amount of 0.1-0.7 percent by weight based on said filament.

5. Textile products made from melt-spun titanium dioxidecontaining polyamide filaments containing dispersed through their structure in an amount of 0.0l-l percent by weight, based on said filaments, titanium dioxide particles consisting essentially of particles of diameters 0.1-7 microns, of which 10-70 percent by weight consists of coarse particles of diameters 0.8-7 microns, said titanium dioxide particles having two distributuion peaks in their particle size distribution, a first peak in the range of0.2-0.5 microns and a second peak in the range of l-6 microns.

7 8 ofO. l-0.7 percent based on said filaments.

7. Textile products according to claim 6 wherein said second peak of the particle size distribution falls within the particle diameter range of 2-5 microns. 

2. The synthetic filament according to claim 1 wherein said titanium dioxide particles consists essentially of those of particle diameters 0.1-7 microns of which 15-60 percent by weight consists of said coarse particles of particle diameter range 1-7 microns.
 3. A synthetic filament according to claim 1 wherein the second of said peaks falls within the range of 2-5 microns.
 4. A synthetic filament according to claim 1 wherein said titanium dioxide particles are contained dispersed in the melt-spun synthetic filament in an amount of 0.1-0.7 percent by weight based on said filament.
 5. Textile products made from melt-spun titanium dioxide-containing polyamide filaments containing dispersed through their structure in an amount of 0.01-1 percent by weight, based on said filaments, titanium dioxide particles consisting essentially of particles of diameters 0.1-7 microns, of which 10-70 percent by weight consists of coarse particles of diameters 0.8-7 microns, said titanium dioxide particles having two distributuion peaks in their particle size distribution, a first peak in the range of 0.2-0.5 microns and a second peak in the range of 1-6 microns.
 6. Textile products according to claim 5 wherein said coarse particles occupy 15-60 percent by weight of the total amount of said titanium dioxide particles, said titanium dioxide particles being contained dispersed in said filaments in an amount of 0.1-0.7 percent based on said filaments.
 7. Textile products according to claim 6 wherein said second peak of the particle size distribution falls within the particle diameter range of 2-5 microns. 